Within the cytoskeleton there are also molecular motors that generate internal stresses [1]}, [2]}, [3]}, which may alter the rheological properties of living cells [4]}, [5]}, [6]}. Recently, it has been shown experimentally that the apparent scaling exponent of the linear shear modulus in reconstituted actin networks with transient crosslinks can be further reduced and systematically varied over the range of \(0.1\lesssim \beta \le 0.5\)  by an applied external stress [7]}.
. When applied to transient networks, aside from the stress-stiffening response, external stress solidifies the network [8]}, suppressing both stress relaxation and reducing the apparent exponent of the frequency-dependent nonlinear shear modulus [7]}. This provides a possible explanation for the weak scaling exponent observed in living cells, as living cells are intrinsically under internal stress generated by molecular motors or other active processes [1]}, [11]}, [12]}, [13]}, although a microscopic model for how stress qualitatively changes the dynamics is still lacking.
